DESCRIPTION This application examines the mechanism by which chromium (VI) interacts with endothelial cell nitric oxide synthase (eNOS) and the consequences this interaction has on endothelial cell adhesive properties. It has been previously shown that Cr(VI) can enter cells and increase intracellular oxidative stress by a redox cycling mechanism. Preliminary studies demonstrate that purified eNOS reduces Cr(VI) to Cr(V) and establishes a redox cycle for the generation of superoxide anion. Increases in oxidative stress have been linked to tissue injury and organ damage such as lung injury, interstital pulmonary disease and pulmonary hypertension. Many of the process taking place in these disease states involve activation of pulmonary vascular endothelial cells. Preliminary studies show that low concentrations of Cr(VI) activate cultured endothelial cells to increase ICAM-1 expression by 6-7 fold. Monocytes and PMN are recruited by sites of inflammation and injury when endothelial cells express GMP-140 acutely in minutes and up-regulate the expression of ICAM-1, VCAM-1 and E-selectin over many hours. Increased expression of these adhesion molecules is, in part, regulated by increases in NF-kB and fos/jun complexes which have both been shown to be activated by increases in oxidative stress. Increases in endothelial cell expression of adhesion molecules is one of the earliest steps in the recruitment of mononuclear and polymorphonuclear cells (PMN) to the vessel wall in acute and chronic injury and atherogenesis. As the activation of endothelial cells eventually leads to the shedding of these adhesion molecules, measurements of circulating concentrations may provide a sensitive and specific biomarker for monitoring the effects of redox cycling xenobiotics and pollutants. Accordingly, it is proposed to (1) Determine the mechanisms by which eNOS interacts with Cr(VI) to increase the generation of reactive oxygen species. (2) Determine the effects of Cr(VI) on endothelial cell oxidant balance with respect to the generation of nitric oxide, superoxide anion and formation of peroxynitrite. (3) Determine the effects of Cr(VI) on the temporal expression of adhesion molecules in endothelial cells with respect to shedding, surface expression and transcriptional regulation.